Those of you that have done the prism matrix, do you need to add more abalone shells or does it already have enough in the mix? Does it sparkle a lot in the sunlight? Also, if you have used glass tile with it to border your tanning ledges/steps, did it turn out ok? One of the plaster companies said that they did not recommend it, but the one we are going with didn't say one way or the other. This is what we have picked out and I really want to keep the glass tiles. I'm a little worried that the tile doesn't go very well with everything else? What do you think??